Automotive sound-absorbing material

ABSTRACT

A thin and light-weight automotive sound-absorbing material with a superior sound-absorbing property, which can be used, for example, for automotive insulator to keep the interior of an automobile quiet. This automotive sound-absorbing material has a laminate structure comprising a sound-absorbing layer, an intermediate layer, and a sound-absorbing layer. The intermediate layer comprises a film made of thermoplastic resin with a thickness of 10 to 100μ, on which small pores are uniformly opened in such a manner that the aperture ratio would be 0.05 to 5%. The sound-absorbing layers comprise an aggregate of fibers such as felt, glass wool, etc. or porous synthetic resin layer, such as urethane foam, etc.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates to a light-weight and thin automotive sound-absorbing material with a superior sound-absorbing property that can be used, for example, for automotive insulator provided on the floor, etc. of an automobile for keeping the interior of the automobile quiet.

2. Discussion of the Background Art

Light-weight sound-absorbing materials based on felt are in the mainstream of the recent automotive sound-absorbing materials for reason of reducing the weight of the car body. While felt excels in sound-absorbing property, it has inferior sound-insulating property. Felt has therefore been crushed to reduce the air permeability in order to improve the sound-insulating property in the prior art.

It was however difficult to give uniform air permeability throughout the entire surface of the felt, since the control of air permeability by crushing the felt resulted in the partial unevenness of the basis weight of the felt. For example, it is necessary to crush the felt to a thickness of 5 mm to control the air permeability of a felt with a basis weight of 1200 g/m² to 10 cc/cm²/sec, but the attempt to obtain said air permeability resulted in a notable unevenness of the air permeability in some parts of the felt, as shown in Table 1, thereby causing the risk of deteriorating both the sound-insulating property and the sound-absorbing property.

Table 1 shows the result of measuring the air permeability of randomly chosen 10 measurement points of a 2 m² felt crushed to a thickness of 5 mm.

TABLE 1 {circle around (1)} {circle around (2)} {circle around (3)} {circle around (4)} {circle around (5)} {circle around (6)} {circle around (7)} {circle around (8)} {circle around (9)} {circle around (10)} AV 3σ 10.8 12.3 11.4 9.3 11.3 12.7 13.3 10.3 11.6 12.3 11.5 3.58

The sound-insulating panel disclosed in the undermentioned JP Patent Application Disclosure No. 11-254570 is obtained by providing a film layer heat-fused between the body of the panel and the sound-absorbing material.

The sound-absorbing integrally molded panel disclosed in JP Patent Application Disclosure No. 2002-0864 is obtained by adhering the body of the panel and the sound-absorbing material via pores provided on the film.

Although these sound-insulating or sound-absorbing structure disclosed in the prior art documents is capable of keeping the airtightness by the film, the sound-absorbing property could not be improved due the lack of air permeability. And although the engine noise could be insulated by using these structures for dash panels, their sound-absorbing property was insufficient for absorbing the noise of the interior of an automobile.

SUMMARY OF THE DISCLOSURE

A light-weight and thin automotive sound-absorbing material with a superior sound-absorbing property.

A sound-absorbing material with a laminate structure comprising a sound-absorbing layer, an intermediate layer, and a sound-absorbing layer, characterized in that the intermediate layer comprises a film with a thickness of 10 to 100μ, on which small pores are uniformly opened in such a manner that the aperture ratio would be 0.05 to 5%.

Preferably, the intermediate layer is a film made of thermoplastic resin and the sound-absorbing layer comprises an aggregate of fibers. The sound-absorbing layer comprises a porous synthetic resin layer. The adhesive layer typically comprising low-melting resin is laminated to at least one side of the film made of thermoplastic resin, and that the adhesive layer is heated and fused to the sound-absorbing layer. The adhesive layer is a low-melting resin with a melting point of 200° C. or lower.

The sound-absorbing layer has a thickness of 0.5 to 40 mm and a basis weight of 100 to 1500 g/m², and that the intermediate layer is a film made of thermoplastic resin to which small pores with diameters of 0.5 to 5 mm are formed with a pitch of 3 to 30 mm.

The automotive sound-absorbing material of the present disclosure is light-weight and thin, and since sound permeates the film and is absorbed uniformly by the entire surface of both sound-absorbing layers, a superior sound-absorbing property can be obtained. The automotive sound-absorbing material of the present disclosure is therefore capable of keeping the interior of an automobile quiet by absorbing noise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a longitudinal section of the automotive sound-absorbing material of the present disclosure.

FIG. 2 is a schematic representation of a longitudinal section of the intermediate layer of the automotive sound-absorbing material of the present disclosure.

FIG. 3 is a schematic representation of a longitudinal section of the intermediate layer of the automotive sound-absorbing material of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, the automotive sound-absorbing material of the present disclosure has a laminate structure comprising a sound-absorbing layer (1), an intermediate layer (2), and another sound-absorbing layer (3). The sound absorbing layers (1, 3) comprises an aggregate of fibers such as felt, glass wool, etc. or a porous synthetic resin layer such as urethane foam, etc. and its thickness is set to 0.5 to 40 mm and the basis weight to 100 to 1500 g/m². The intermediate layer (2) comprises a film made of thermoplastic resin such as polyethylene, polypropylene, nylon, polyester, etc., on which small pores with diameters of 0.5 to 5 mm are formed with a pitch of 3 to 30 mm so that the aperture ratio would be 0.05 to 5%.

As shown in FIG. 2, in the intermediate layer (2), an adhesive layer (5) comprising low-melting resin with a melting point of 200° C. or lower, such as polyethylene, unsaturated polyester, etc., is laminated to at least one side of the film (4) made of thermoplastic resin by inflation.

The aforesaid small pores are formed by pressing the film (4) made of thermoplastic resin to a heated roll having numbers of needle-like spikes formed on its outer circumferential surface. And after melting the adhesive layer (5) by heating the same for 1 minutes by applying hot wind of 170° C., which is a felt-molding temperature, and the adhesive layer (5) is superposed and pressed onto the felt to adhere the film (4) made of thermoplastic resin to the felt.

As shown in FIG. 3, it is also possible to laminate adhesive layers (5, 6) comprising low-melting resin such as polyethylene, unsaturated polyester, etc., to both sides of the film (4) made of thermoplastic resin to adhere the film (4) made of thermoplastic resin to the sound-absorbing layers (1, 3).

By further laminating sound-absorbing layers to 4 layers, 5 layers, etc., the automotive sound-absorbing material of the present disclosure can absorb noise and keeping the interior of an automobile quiet.

EXAMPLE 1

In this example, felt with a basis weight of 500 g/m² mainly made of PET fiber of 2 to 6 dtex was used as the sound-absorbing layers (1, 3), and as the intermediate layer (2), a layer obtained by laminating a 20 μ-thick adhesive layer (5) comprising unsaturated polyester to a 20 μ-thick film (4) made of thermoplastic resin comprising polyethylene was used. Small pores with a diameter of 1 mm were formed onto the film (4) made of thermoplastic resin with a pitch of 5 mm, and the obtained pored film was adhered to the felt. The air-permeability of a surface area of 2 m² of the obtained sound-absorbing material was measured at randomly chosen 10 measurement points. The results are shown in Table 2 in the same manner as in Table 1:

TABLE 2 {circle around (1)} {circle around (2)} {circle around (3)} {circle around (4)} {circle around (5)} {circle around (6)} {circle around (7)} {circle around (8)} {circle around (9)} {circle around (10)} AV 3σ 10.8 10.3 10.4 10.3 11.0 10.7 10.3 10.3 10.6 10.3 10.5 0.77

As shown under 3σ in Table 2, the scattering of the air-permeability could be remarkably reduced in the example of the disclosure by adhering pored film to the felt, thereby making the air-permeability of the entire surface of the felt nearly uniform.

A thin pored film is sandwiched as an intermediate layer between the two sound-absorbing layers made of felt in the automotive sound-absorbing material of the present disclosure, and the pored film vibrates in harmony with the air vibration, which is the sound component, thereby absorbing the sound-wave energy. The automotive sound-absorbing material of the present disclosure therefore exhibits excellent sound-absorbing property.

Namely, by providing an intermediate layer comprising a thin pored film between two sound-absorbing layers made of felt, the film is vibrated freely by the sound wave, thereby weakening the sound wave energy, and since the entire surface of the film has nearly uniform air permeability, sound is absorbed uniformly by the entire surface of the felt on both sides of the film, realizing the excellent sound-absorbing property.

By this reason, fully satisfying sound-absorbing effect can be obtained even when using a thin felt with a basis weight of 500 g/m², as the one used in the example of the disclosure. And by providing the sound-absorbing material of the present disclosure to the floor surface and ceiling surface inside an automobile, noise can be absorbed and the interior of the automobile can be kept quiet. 

1. An automotive sound-absorbing material having a laminated structure composed of a sound-absorbing layer, an intermediate layer, and a sound-absorbing layer, wherein the intermediate layer comprises a film with a thickness of 10 to 100μ, on which small pores are uniformly opened in such a manner that the aperture ratio would be 0.05 to 5%.
 2. The automotive sound-absorbing material according to claim 1, wherein the intermediate layer is a film made of thermoplastic resin.
 3. The automotive sound-absorbing material according to claim 1, wherein the sound-absorbing layer comprises an aggregate of fibers.
 4. The automotive sound-absorbing material according to claim 1, wherein the sound-absorbing layer comprises a porous synthetic resin layer.
 5. The automotive sound-absorbing material according to claim 2, wherein an adhesive layer comprising low-melting resin is laminated to at least one side of the film made of thermoplastic resin, and the adhesive layer is heated and fused to the sound-absorbing layer.
 6. The automotive sound-absorbing material according to claim 5, wherein the adhesive layer is a low-melting resin with a melting point of 200° C. or lower.
 7. The automotive sound-absorbing material according to claim 1, wherein the sound-absorbing layer has a thickness of 0.5 to 40 mm and a basis weight of 100 to 1500 g/m², and the intermediate layer is a film made of thermoplastic resin to which small pores with diameters of 0.5 to 5 mm are formed with a pitch of 3 to 30 mm. 